MAX1666X

19-1465; Rev 2; 12/03 Advanced Lithium-Ion Battery-Pack Protector General Description The MAX1666 provides complete protection against overvoltage, undervoltage, overcharge current, overdischarge current, and cell mismatch for 2-cell to 4-cell lithium-ion (Li+) battery packs. The voltage of each cell in the battery pack is checked and compared to the programmable threshold and to the other cells in the pack. The MAX1666 protects the battery pack in an overcurrent condition by disconnecting the pack from the load at a programmable limit. On-chip power MOSFET drivers control external P-channel MOSFETs to disconnect the cells from external terminals when faults occur. The MAX1666 employs a unique timing scheme that allows three modes of operation for optimal performance and battery power conservation. The MAX1666 can operate in a stand-alone configuration or in conjunction with a microcontroller. It is available in four versions: the S version monitors two Li+ cells, the A and V versions monitor three cells, and the X version monitors four cells. When the charge path is disabled by the charge control pin, the MAX1666A reduces current consumption compared to the MAX1666S/V/X. Features ♦ Overvoltage Protection Programmable Limits from +4.0V to +4.4V Accurate to ±0.5% ♦ Undervoltage Protection Programmable Limits from +2.0V to +3.0V Accurate to ±2.5% ♦ Cell Mismatch Protection Programmable Limits from 0 to 500mV Accurate to ±10% ♦ Overcharge Current Protection ♦ Overdischarge Current Protection ♦ Low 30µA (typ) Operating Supply Current ♦ Low 1µA (max) Standby Current ♦ +28V (max) Input Voltage ♦ Available in Small 16-Pin QSOP (MAX1666S) and 20-Pin QSOP (MAX1666A/V/X) Packages MAX1666A/S/V/X Applications 2/3/4-Cell Lithium-Ion Battery Pack PART MAX1666SEEE MAX1666AEEP PART MAX1666S MAX1666A/V MAX1666X NUMBER OF Li+ CELLS 2 3 4 MAX1666VEEP MAX1666XEEP Ordering Information TEMP RANGE -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C PIN-PACKAGE 16 QSOP 20 QSOP 20 QSOP 20 QSOP Selector Guide Typical Operating Circuits appear at end of data sheet. Pin Configurations TOP VIEW SRC 1 DSO 2 TKO 3 CGO 4 B2P 5 BIP 6 GND 7 PKN 8 16 VCC 15 REF 14 OVA SRC 1 DSO 2 TKO 3 CGO 4 B3P 5 B3P 6 B2P 7 B1P 8 GND 9 PKN 10 20 UVO 19 VCC 18 REF 17 OVA SRC 1 DSO 2 TKO 3 CGO 4 B4P 5 B3P 6 B2P 7 B1P 8 GND 9 PKN 10 20 UVO 19 VCC 18 REF 17 OVA MAX1666S 13 UVA 12 MMA 11 PKF 10 CGI 9 DSI MAX1666A/V 16 UVA 15 MMA 14 WRN 13 PKF 12 CGI 11 DSI MAX1666X 16 UVA 15 MMA 14 WRN 13 PKF 12 CGI 11 DSI QSOP QSOP QSOP ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X ABSOLUTE MAXIMUM RATINGS SRC, DSO, TKO, CGO, UVO, PKF, WRN to GND ...-0.3V to +28V VCC, REF, OVA, UVA, MMA to GND ........................-0.3V to +6V B4P to B3P ...............................................................-0.3V to +6V B3P to B2P ...............................................................-0.3V to +6V B2P to B1P ...............................................................-0.3V to +6V B1P to GND ..............................................................-0.3V to +6V PKN to GND...........................................................................±2V VCC, CGI, DSI to PKN...............................................-0.3V to +6V Continuous Power Dissipation (TA = +70°C) 16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW 20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Charge-Mode Detection Threshold SYMBOL VSRC - VB_P VSRC - VB_P = 1V, VCGI = VDSI = GND SRC Supply Current MAX1666A only, VSRC - VB3P = 1V, VCGI = 3V, VDSI = GND MAX1666A only, VSRC - VB3P = 1V, VDSI = 3V, VCGI = GND Supply Current Shutdown Supply Current VCC Output Voltage VCC Undervoltage-Lockout Threshold Reference Output Voltage Overvoltage Threshold Overvoltage-Threshold Hysteresis UVA = GND Undervoltage Threshold Undervoltage-Threshold Hysteresis Cell voltage falling VUVA = VREF / 2 UVA = REF 2.925 1.950 VREF Pulse on Cell voltage rising OVA = GND VOVA = VREF / 2 OVA = REF 4.378 3.980 ISUP ISHDN VCC RLOAD ≥ 665Ω, 2V < VCELL < 4.4V 3.09 2.7 3.25 2.85 1.221 4.000 4.2 4.400 200 2.000 2.500 3.000 100 3.075 mV 2.050 V 4.422 mV 4.020 V No faults, long-time average current from the top battery terminal B_P CONDITIONS MIN 1 2 2 2 30 10 5 5 45 1 3.41 3.0 µA µA V V V µA TYP MAX UNITS V 2 _______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector ELECTRICAL CHARACTERISTICS (continued) (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER WRN Early-Warning Threshold WRN Early-Warning-Threshold Hysteresis OVA, UVA, MMA Input Current Cell Mismatch Threshold PKN to GND OverdischargeCurrent Threshold PKN to GND Overcharge-Current Threshold Overcurrent Fault-Timer Delay Overdischarge/OverchargeCurrent Fault-Blanking Time DSO, CGO, UVO Output Sink Current DSO, CGO Output Source Current DSO, CGO, UVO Leakage Current TKO Pulldown Resistance, MAX1666S/V/X TKO Sink Current, MAX1666A Only TKO Leakage Current, MAX1666A Only Minimum B3P Voltage for TKO Low, MAX1666A Only TKO Source Current DSI, CGI Input High Voltage DSI, CGI Input Low Voltage DSI, CGI Input Current WRN Sink Current PKF Sink Current PKF, WRN Leakage Current Undervoltage, Overvoltage, or Mismatch Fault, to DSO, CGO, TKO Transition Delay tF-DELAY V TKO = 16V V TKO = 16V, VCGI = 3V VSRC = VB3P + 1V, ITKO = 0.5mA TKO = GND Referenced to PKN Referenced to PKN VDSI, VCGI = 5V Fault condition, V WRN = 0.4V Fault condition, V PKF = 0.4V V PKF = V WRN = 27V Fault persistent for four consecutive sample periods 180 320 2 4 4 8 0.2 460 1 2 0.45 1 2.4 8 tP-DELAY tI-DELAY No faults, V DSO = V CGO = VUVO = 1V to 27V V DSO = VSRC - 4V and V CGO = VSRC - 4V, fault condition V DSO = V CGO = VUVO = 27V, fault condition 100 1 200 2.5 1 3.6 OVA, UVA, MMA = REF MMA = GND All cells > 2V VMMA = VREF / 2 MMA = REF ±450 270 -220 330 1.6 20 2 SYMBOL CONDITIONS Above undervoltage threshold, cell voltage falling MIN TYP 100 200 0.1 ±0 ±250 ±500 300 -200 550 2.4 30 10 0.2 ±550 330 -180 770 3.2 40 mV mV ms ms µA mA µA kΩ mA µA V mA V V µA mA mA µA ms mV 20 MAX UNITS mV mV nA MAX1666A/S/V/X _______________________________________________________________________________________ 3 Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X ELECTRICAL CHARACTERISTICS (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER Charge-Mode Detection Threshold SYMBOL VSRC - VB_P VSRC - VB_P = 1V, VCGI = VDSI = GND SRC Supply Current MAX1666A only, VSRC - VB3P = 1V, VCGI = 3V, VDSI = GND MAX1666A only, VSRC - VB3P = 1V, VDSI = 3V, VCGI = GND Supply Current Shutdown Supply Current VCC Output Voltage VCC Undervoltage-Lockout Threshold Overvoltage Threshold Undervoltage Threshold OVA, UVA, MMA Leakage Cell Mismatch Threshold PKN to GND OverdischargeCurrent Threshold PKN to GND Overcharge-Current Threshold Overcurrent Fault-Timer Delay Overdischarge/OverchargeCurrent Fault-Blanking Time DSO, CGO, UVO Output Sink Current DSO, CGO Output Source Current DSO, CGO, UVO Leakage Current tP-DELAY tI-DELAY No faults; V DSO, V CGO, VUVO = 1V to 27V V DSO = VSRC - 4V and V CGO = VSRC - 4V, fault condition V DSO = V CGO = VUVO = 27V, fault condition OVA = GND OVA = REF UVA = GND UVA = REF OVA, UVA, MMA = REF All cells > 2V, MMA = REF ±450 270 -220 330 1.6 20 2 0.2 ISUP ISHDN VCC RLOAD ≥ 665Ω, 2V < VCELL < 4.4V 3.09 2.7 3.975 4.373 1.950 2.925 No faults, long-time average current from the top battery terminal B_P CONDITIONS MIN 1 10 5 5 45 1 3.41 3.0 4.025 4.427 2.050 3.075 20 ±550 330 -180 770 3.2 40 µA µA V V V V nA mV mV mV ms ms µA mA µA µA TYP MAX UNITS V 4 _______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector ELECTRICAL CHARACTERISTICS (VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER TKO Pulldown Resistance, MAX1666S/V/X TKO Sink Current, MAX1666A Only Minimum B3P Voltage for TKO Low TKO Source Current DSI, CGI Input High Voltage DSI, CGI Input Low Voltage DSI, CGI Input Current WRN Sink Current PKF Sink Current PKF, WRN Leakage Current Undervoltage, Overvoltage, or Mismatch Fault, to DSO, CGO, TKO Transition Delay tF-DELAY V TKO = 16V VSRC = VB3P + 1V, ITKO = 0.5mA TKO = GND Referenced to PKN Referenced to PKN VDSI = VCGI = 5V Fault condition, V WRN = 0.4V Fault condition, V PKF = 0.4V V PKF = V WRN = 27V Fault persistent for four consecutive sample periods 180 2 4 0.2 460 1 2 0.45 1 SYMBOL CONDITIONS MIN 100 1 3.6 TYP MAX UNITS kΩ mA V mA V V µA mA mA µA ms MAX1666A/S/V/X Note 1: Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 5 Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX1666toc01 SUPPLY CURRENT vs. TEMPERATURE MAX1666toc02 UNDERVOLTAGE THRESHOLD vs. TEMPERATURE UVA = REF UNDERVOLTAGE THRESHOLD (V) MAX1666toc03 770 VCELL = 3.6V 760 SUPPLY CURRENT (nA) 750 740 730 720 710 700 -40 -20 0 20 40 60 80 35 VCELL = 3.6V 33 SUPPLY CURRENT (µA) 3.0015 3.0010 31 29 3.0005 27 25 100 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) TEMPERATURE (°C) 3.0000 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) OVERVOLTAGE THRESHOLD vs. TEMPERATURE MAX1666toc04 MISMATCH VOLTAGE THRESHOLD vs. TEMPERATURE MAX1666toc05 OVERCHARGE THRESHOLD vs. TEMPERATURE MAX1666toc06 4.400 OVA = REF UNDERVOLTAGE THRESHOLD (V) 501 MISMATCH VOLTAGE THRESHOLD (mV) MMA = REF 500 499 498 497 496 495 -40 -20 0 20 40 60 80 203 OVERCHARGE THRESHOLD (mV) 202 4.395 201 4.390 200 4.385 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 199 100 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) TEMPERATURE (°C) OVERDISCHARGE THRESHOLD vs. TEMPERATURE MAX1666toc07 OVERDISCHARGE PROTECTION MAX1666toc08 OVERDISCHARGE RECOVERY TIME MAX1666toc09 302 OVERDISCHARGE THRESHOLD (mV) 301 300 299 298 297 296 295 -40 -20 0 20 40 60 80 PKN (0.5V/div) PKN (0.5V/div) tI-DELAY DSO (10V/div) DSO (10V/div) tP 100 1ms/div 100ms/div TEMPERATURE (°C) 6 _______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) OVERCHARGE MAX1666toc10 MAX1666A/S/V/X OVERVOLTAGE FAULT 4.5V B1P 123 4 123 4 MAX1666toc11 PKN (0.5V/div) 4.1V REF (1V/div) tP-DELAY CGO (10V/div) tF-DELAY tF-DELAY CGO (10V/div) 100ms/div 100ms/div VCELL2 = VCELL3 = VCELL4 = 4.15V, OVERVOLTAGE THRESHOLD = 4.4V UNDERVOLTAGE FAULT MAX1666toc12 CELL MISMATCH FAULT 3.4V 2.9V 1 REF (1V/div) PKF (10V/div) 234 1 2 3 4 MAX1666toc13 3.4V 2.9V 1 23 4 123 4 B1P REF (1V/div) WRN (10V/div) tF-DELAY tF-DELAY B1P tF-DELAY tF-DELAY DSO (10V/div) DSO (10V/div) 100ms/div VCELL2 = VCELL3 = VCELL4 = 3.35V, UNDERVOLTAGE THRESHOLD = 3.0V, UVA = REF 100ms/div VCELL2 = VCELL3 = VCELL4 = 3.6V, CELL MISMATCH THRESHOLD = 0.5V, MMA = REF UNDERVOLTAGE FAULT WITHOUT CHARGE SOURCE (VSRC < VB4P + 1V) 3.4V 2.9V MAX1666toc14 DSO (10V/div) B1P REF (1V/div) VCC (2V/div) 100ms/div VCELL2 = VCELL3 = VCELL4 = 3.35V, UNDERVOLTAGE THRESHOLD = 3.0V, UVA = REF _______________________________________________________________________________________ 7 Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X Pin Description PIN NAME MAX1666X 1 2 MAX1666A/V 1 2 MAX1666S 1 2 SRC DSO Charge Source Input. Provides current for gate drivers DSO, TKO, CGO, and UVO. Discharge Driver Output. Drives external P-channel MOSFET to control discharge. Trickle-Charge Driver Output. Drives external P-channel MOSFET to control trickle-charge current. MAX1666A requires an external pullup resistor of 470kΩ Fast-Charge Driver Output. Drives external P-channel MOSFET to control fast charge. Cell 4 Positive Input. Power supply input for MAX1666X. Cell 3 Positive Input. Power supply input for MAX1666A/V. Cell 2 Positive Input. Power supply input for MAX1666S. Cell 1 Positive Input Ground Battery Pack Negative Terminal. Connect to bottom of current-sense resistor. Ground reference for logic inputs DSI and CGI. Discharge Control Input Charge Control Input Pack Fail Output. PKF goes low when any cell voltage exceeds the mismatch threshold or when a shorted cell is detected. Undervoltage/Overvoltage Warning Output Mismatch Adjust Input. Set the mismatch threshold by a resistordivider from REF to GND. Undervoltage Adjust Input. Set the undervoltage threshold with a resistor-divider from REF to GND. Overvoltage Adjust Input. Set the overvoltage threshold with a resistor-divider from REF to GND. Reference Voltage Output. Minimize PC board stray capacitance on this node. 3.3V Linear Regulator Output. Bypass with a 0.47µF min capacitor to GND. Undervoltage Fault Output FUNCTION 3 3 3 TKO 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 4 — 4 — — CGO B4P B3P B2P B1P GND PKN DSI CGI PKF WRN MMA UVA OVA REF VCC UVO 5, 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 5 6 7 8 9 10 11 — 12 13 14 15 16 — 8 _______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X CGO SRC SRC DSI D Q RB CK "1" Q D RB CK N "1" DSO N CGI OV_FAULT CM_FAULT UV_FAULT CQI_FAULT N UV_FAULT CM_FAULT DQY_FAULT 30µA 30µA N MAX1666 50kHz OSC B4P B3P B2P BIP GND CELL VOLTAGE SELECTOR CMP_P OSC GND LATCH_WRN REG EARLY WARNING WARNING GND LATCH_OV STATE MACHINE LATCH_UV REG OVERVOLTAGE OV-FAULT OVA UVA MMA REF 1.221V THRESHOLD VOLTAGE SELECTOR CMP_N CMP REG UNDERVOLTAGE UV-FAULT LATCH_CM REG CELL MISMATCH CM-FAULT PKF N GND 200mV PKN CQI_HI 550ms TIMER SET/RESET DQI_HI 300mV GND SRC CHARGE 1V B4P UV_FAULT BIAS TKO UVO CM_FAULT UV_FAULT CGI OV_FAULT CM_FAULT 30µA GND N SHUTDOWN 3.3V LINEAR REG. VCC DQI_FAULT B4P CQI_FAULT OV_FAULT WARNING UV_FAULT N WRN Figure 1. Functional Diagram _______________________________________________________________________________________ 9 Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X BATTERY CONNECTED YES SHUTDOWN VSRC < VB4P + 1V VSRC > VB4P + 1V VCC > 2.85V NO YES (DISCHARGE CURRENT · RCS) 300mV (>2.4ms) (CHARGE CURRENT · RCS) 200mV (>2.4ms) CHARGE CURRENT MONITOR OVERDISCHARGE DSO = H RESET RESET DS0 = L CGO = L OVERCHARGE CGO = H 550ms DELAY STANDBY 80ms VCELL < UNDERVOLTAGE THRESHOLD YES CHECK VREF NO LATCH UVF = ‘1’ CELL MISMATCH SAMPLE 2.5ms YES NO LATCH MMF = ‘1’ NO VREF > 1.1V YES VCELL < UNDERVOLTAGE WARNING THRESHOLD NO YES LATCH UVW = ‘1’ VCELL > OVERVOLTAGE THRESHOLD YES NO LATCH OVF = ‘1’ UVF = ‘1’ AND VSRC < VB4P + 1V NO YES GO TO TABLE 2 Figure 2. Cell Fault Monitor 10 ______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector REF R1 R3 R5 MAX1666 OVA UVA MMA R2 GND R4 R6 parator monitoring VSRC and the top-cell voltage. The MAX1666 remains in shutdown mode as long as VSRC is less than the top-cell voltage. When SRC is connected to an external charger and VSRC is 1V above the top-cell voltage, the device goes into standby mode. The MAX1666 returns to shutdown mode under two conditions: the battery is disconnected and then reconnected, or the device detects an undervoltage fault and no charge source. Normal Mode The standby state activates the bias circuitry, overcurrent comparator, and timer. The standby state lasts 80ms, then the MAX1666 goes into the sample state for 2.5ms. Within the 2.5ms, the MAX1666 checks for overvoltage, undervoltage, and mismatch between cells sequentially, and it stores the results in internal latches. The MAX1666 drives the outputs according to the faults (if any) detected by reading the latches (Figure 2) at the end of the sample state. Then the MAX1666 returns to the standby state. MAX1666A/S/V/X Figure 3. Using an External Resistor-Divider to Adjust Overvoltage Threshold Detailed Description The MAX1666 battery-pack protectors supervise the charging and discharging processes of Li+ battery cells. Designed for 2-, 3-, and 4-cell applications, these devices monitor the voltage across each cell to provide protection against undervoltage, overvoltage, and overcurrent damage. Control pins C GO , T KO , and D SO allow control of external MOSFET gates. This allows fast charging, trickle charging, and discharging processes (see the Typical Operating Circuits). The voltage of each cell is measured individually. Also, each cell is measured differentially between every other cell of the pack. The MAX1666 contains a state machine, a voltage regulator, an oscillator, and other logic functions to selectively drive C GO , UVO, T KO , D SO , W RN , and P KF (Figure 1). Overvoltage Protection The MAX1666 provides overvoltage protection to avoid overcharging of any cell. When any cell is at overvoltage, CGO and TKO go high, turning off the external MOSFETs and stopping the charging process (see the Typical Operating Circuits). WRN goes low. Overvoltage is set when any cell voltage exceeds the overvoltage threshold. Overvoltage threshold is linearly adjustable through an external 1% resistor-divider (Figure 3) from REF. Determine the overvoltage threshold (VOVT) required. VOVT must be between 4V and 4.4V. Set RTOTAL = R1 + R2 = 1MΩ. Calculate R1 and R2 as follows: R2 = [(VOVT - 4V) / (4.4V- 4V)] · RTOTAL R1 = RTOTAL - R2 Modes of Operation Shutdown Mode The MAX1666 goes into shutdown mode when a battery pack is first connected. The quiescent current is less than 1µA. All circuitry is inactive except the com- Table 1. Operating Modes MODE STATE Standby Normal Sample Shutdown — 2.5 — 250 0.7 All circuitry active. All circuitry inactive. Device enters shutdown when it detects an undervoltage fault and VSRC < VTOP-CELL + 1V (no charge source). 11 TIME (ms) 80 TYPICAL QUIESCENT CURRENT (µA) 24 CONDITION Only bias circuitry, overcurrent comparator, and timer are active. ______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X B4P I4 + V4 + V3 ICB = V4 R B3P I3P I3 B2P I2P + V2 I2 B1P I1P + V1 I1 + V1 + V2 V1 R + V3 V2 R + V4 V3 R ICB = V4 R ICB = V4 R threshold (VUVT) accuracy including the internal undervoltage-threshold accuracy (±2.5%) is ±3.2%. Undervoltage Warning When any cell drops to 100mV above the undervoltage threshold, WRN goes low. WRN returns high when all cells are 300mV above the undervoltage threshold. Cell-Mismatch Protection The MAX1666 disables charging or discharging when mismatch occurs. When any two cells are mismatched, TKO , CGO , UVO, and DSO go high, turning off the external MOSFETs. PKF goes low. PKF has a strong pulldown current (>4mA), and can be used to control an external thermal fuse. The cell-mismatch threshold is linearly adjustable through an external resistor-divider (Figure 3) from REF. Determine the cell-mismatch threshold (VCMT) required. VCMT has to be between 0 and 500mV. Set RTOTAL = R5 + R6 = 1MΩ. Calculate R5 and R6: R6 = (VCMT / 500mV) RTOTAL R5 = RTOTAL - R6 Maximum mismatch of a 1% external resistor-divider is ±2%. The total external adjusted cell-mismatch threshold accuracy, including the internal cell-mismatch threshold accuracy (±10%), is ±12%. R R R R V4 R Figure 4. Cell Voltage Sampling Maximum mismatch of 1% external resistor-dividers is ±2%. The external adjusted overvoltage-threshold accuracy includes the internal overvoltage-threshold accuracy (±0.5%) and the error due to the external resistor-divider multiplied by maximum adjustment: ±2% 4.4V − 4.0V 4.4V = ± 0.2% Cell Voltage Sampling The MAX1666 does not introduce cell mismatch. When the battery cells are matched, the MAX1666 draws close to zero current from the intermediate cells. Figure 4 shows a simplified diagram of the voltage sampling scheme: B4P: I4 = 3ICB + V4 / R = 4V4 / R = BAT4 current B3P: I3 = I3P + I4 = BAT3 current I3P + ICB = V3 / R ⇒ I3P = V3 / R - V4 / R I3 = I4 + (V3 - V4) / R = (3V4 + V3) / R B2P: I2 = I2P + I3 = BAT2 current I2P + ICB = V2 / R ⇒ I2P = V2 / R - V4 / R I2 = I3 + V2 / R - V4 / R = I4 + (V3 - V4) / R + (V2 - V4) / R = (2V4 + V3 + V2) / R B1P: I1 = I1P + I2 = BAT1 current I1P + ICB = V1 / R ⇒ I1P = V1 / R - V4 / R I1 = I2 + V1 / R - V4 / R = I4 + (V3 - V4) / R + (V2 - V4) / R + (V1 - V4) / R = (V4 + V3 + V2 + V1) / R when V1 = V2 = V3 = V4, I1P = I2P = I3P = 0, and I1 = I2 = I3 = I4 = 4V4 / R The total external adjusted overvoltage-threshold (VOVT) accuracy is ±0.7%. Undervoltage Protection The MAX1666 provides undervoltage protection to avoid overdischarging the cells. When any cell is under voltage, UVO, DSO, and CGO go high, turning off the external charging and discharging MOSFETs. T KO remains low to keep the trickle-charge current on. Undervoltage threshold is linearly adjustable through an external resistor-divider (Figure 3) from REF. Determine the undervoltage threshold (VUVT) required. VUVT must be between 2V and 3V. Set RTOTAL = R3 + R4 = 1MΩ. Calculate R3 and R4 as follows: R4 = [(VUVT - 2V) / (3V - 2V)] RTOTAL R3 = RTOTAL - R4 Maximum mismatch of 1% external resistor-dividers is ±2.0%, and the error due to the external resistor-divider multiplied by maximum adjustment is ±2% (3V - 2V) / 3V = ±0.7%. The total external adjusted undervoltage- 12 ______________________________________________________________________________________ Table 2. Truth Table CONTROL OUTPUTS OCC 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 UVF: Undervoltage fault ODC: Overdischarge current fault 0 H H H 0 H H H L L 0 H H H L 0 H H H L 0 H H H L L L L L L 0 H H H L L 0 H H H L L H H H H H H H 0 H H H L L H 0 H H H L H L 1 PS H H L H L 0 L H H L H L 0 H PS L L H L 0 H L L L H L 0 L PS L L H L 1 PS L L L H L 0 L L L L H L 0 H H H L L H Undervoltage fault early warning Undervoltage fault early warning, overdischarge current fault Undervoltage fault early warning, overcharge current fault Undervoltage fault early warning, disable discharge path Undervoltage fault early warning, disable discharge path, overcharge current fault Undervoltage fault early warning, disable charge path Undervoltage fault early warning, disable charge path, overdischarge current fault Undervoltage fault early warning, disable charge and discharge path Undervoltage fault early warning, mismatch fault Undervoltage fault early warning, mismatch fault, disable discharge path Undervoltage fault early warning, mismatch fault, disable charge path Undervoltage fault early warning, mismatch fault, disable charge and discharge path Undervoltage fault early warning, overvoltage fault, mismatch fault Undervoltage fault early warning, overvoltage fault, mismatch fault, disable discharge path Undervoltage fault early warning, overvoltage fault, mismatch fault, disable charge path Undervoltage fault early warning, overvoltage fault, mismatch fault, disable charge and discharge path OVF: Overvoltage fault CGI: Charge control input MMF: Mismatch fault DSI: Discharge control input 0 H H H L L H 0 H H H L L H 0 H H H L L H 0 H H H L L H 0 H H H L L H 0 H H H L L H Undervoltage fault, mismatch fault, disable charge path Undervoltage fault, mismatch fault, disable charge and discharge path Undervoltage fault, overvoltage fault, mismatch fault Undervoltage fault, overvoltage fault, mismatch fault, disable discharge path Undervoltage fault, overvoltage fault, mismatch fault, disable charge path Undervoltage fault, overvoltage fault, mismatch fault, disable charge and discharge path 0 H H H L L H Undervoltage fault, mismatch fault Undervoltage fault, mismatch fault, disable discharge path 0 H H H L H H Undervoltage fault, disable charge and discharge path 0 H H H L H H Undervoltage fault, disable charge path 0 H H L L H H Undervoltage fault, disable discharge path 0 H H L L H H Undervoltage fault 0 H H H L L H Overvoltage fault, mismatch fault, disable charge and discharge path 0 H H H L L H Overvoltage fault, mismatch fault, disable charge path 0 H H H L L H Overvoltage fault, mismatch fault, disable discharge path 0 H H H L L H Overvoltage fault, mismatch fault 0 H H H L H L Overvoltage fault, disable charge and discharge path 1 PS H H L H L Overvoltage fault, disable charge path, overdischarge current fault 0 L H H L H L Overvoltage fault, disable charge path 0 H H H L H L Overvoltage fault, disable discharge path 1 PS H H L H L Overvoltage fault, overdischarge current fault 0 L H H L H L Overvoltage fault 0 H H H H L H Mismatch fault, disable charge and discharge path 0 H H H H L H Mismatch fault, disable charge path 0 H H H H L H Mismatch fault, disable discharge path 0 H H H H L H Mismatch fault 0 H H H H H L Disable charge and discharge path 1 PS H H H H L Disable charge path, overdischarge current fault 0 L H H H H L Disable charge path 0 H PS L H H L Disable discharge path, overcharge current fault 0 H L L H H L Disable discharge path 0 L PS L H H L Overcharge current fault 1 PS L L H H L Overdischarge current fault 0 L L L H H L Normal operation ODC DSO UVO CGO TKO WRN PKF NOTES DSI 0 0 0 1 1 0 0 1 0 1 0 1 0 0 1 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 0 0 1 1 0 0 1 0 1 0 1 0 1 0 1 CONTROL INPUTS UVW UVF OVF MMF CGI 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 1 1 0 0 0 1 1 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 1 0 0 1 0 1 0 0 1 0 1 0 0 1 1 0 0 0 1 1 0 0 0 1 1 1 0 0 1 1 1 1 1 0 0 0 1 1 0 0 0 1 1 0 0 1 1 1 0 0 1 1 1 0 1 0 1 1 0 1 0 1 1 0 1 1 1 1 0 1 1 1 1 1 1 0 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 1 1 0 0 0 1 1 0 0 0 1 1 0 0 1 0 1 0 0 1 0 1 0 0 1 1 1 0 0 1 1 1 0 1 1 0 1 0 1 1 0 1 0 1 1 1 1 0 1 1 1 MAX1666A/S/V/X ______________________________________________________________________________________ PS: Overcurrent fault pulse sampling. (Output goes high for 500ms then resets low to monitor charge/discharge current. Output goes high again if fault persists.) UVW: Undervoltage fault early warning OCC: Overcharge current fault Advanced Lithium-Ion Battery-Pack Protector 13 Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X Overcharge/Overdischarge Current Protection The MAX1666 checks for overcharge or overdischarge current in standby and sample states. The thresholds are factory preset to 200mV and 300mV, respectively. A charge current makes PKN go below GND. A discharge current makes PKN go above GND. When PKN exceeds the threshold, a fault is acknowledged. CGO goes high when the overcharge threshold is exceeded. DSO goes high when the overdischarge threshold is exceeded. An internal 550ms timer starts. At the end of 550ms, D SO or C GO goes low while the MAX1666 rechecks for an overcharge/overdischarge fault. A persistent fault causes DSO and CGO to return high and restarts the 550ms timer again. Table 3. MOSFET Selection P-CHANNEL MOSFETs IRF7404 IRF7406 Si4431 Si4947 (dual) MAXIMUM DRAIN CURRENT (A) 5.3 4.7 4.5 2.5 EA Truth Table The MAX1666 has a total of eight signal inputs and six outputs. Table 2 lists all the possible states. CGO controls the MOSFET for normal charging of the battery. TKO controls the MOSFET for trickle charge of the cells. DSO controls the discharging MOSFET. Use different MOSFETs to optimize each function depending on the maximum charge and discharge rates. Table 3 lists some suitable MOSFETs in a small 8-pin SO package. Layout Considerations and Bypassing As with all PC board designs, a careful layout is suggested. Minimize lead lengths to reduce losses in the traces. Applications Information Choosing an External MOSFET The external P-channel MOSFETs act as a gated switch to enable or disable the charging/discharging process. 14 ______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector Typical Operating Circuits OVERDISCHARGE PROTECTION P 1 470kΩ 470kΩ 2 DSO P 4 CGO P TRICKLE CHARGE 270Ω OVERCHARGE PROTECTION 3 5 DSI CGI WRN B4P B3P PKF UVO REF 7 8 B2P 20 18 499kΩ 1% 499kΩ 1% 499kΩ 1% 11 12 14 13 SRC VCC 19 0.47µF +3.3V 5mA MAX1666A/S/V/X PACK+ TKO 6 B1P MAX1666X 9 GND PKN 10 17 OVA 16 UVA 15 MMA 499kΩ 1% 499kΩ 1% 499kΩ 1% RSENSE 0.05Ω PACK- ______________________________________________________________________________________ 15 Advanced Lithium-Ion Battery-Pack Protector MAX1666A/S/V/X Typical Operating Circuits (continued) OVERDISCHARGE PROTECTION P PACK+ 470kΩ 470kΩ 2 DSO P 4 CGO P OVERCHARGE PROTECTION 3 5 1 SRC VCC 19 1µF 100kΩ 100kΩ 220kΩ VCC OUT1 OUT2 IN1 IN2 IN3 PACK CONTROLLER 499kΩ 1% 499kΩ 1% 499kΩ 1% GND +3.3V 5mA DSI CGI WRN 12 11 14 13 TRICKLE CHARGE 270Ω TKO B4P B3P PKF UVO REF 20 18 6 7 8 B2P B1P MAX1666X 9 GND PKN 10 17 16 UVA 15 MMA OVA 499kΩ 1% 499kΩ 1% 499kΩ 1% RSENSE 0.05Ω PACK- ___________________Chip Information TRANSISTOR COUNT: 4835 16 ______________________________________________________________________________________ Advanced Lithium-Ion Battery-Pack Protector ________________________________________________________Package Information QSOP.EPS MAX1666A/S/V/X Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17 © 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.